1. Department of Paediatrics, Centre for Paediatric Rheumatology, Asklepios Clinic Sankt Augustin, Sankt Augustin, Germany
2. Medical Faculty, University of Cologne, Cologne, Germany
3. Institute of Medical Statistics and Computational Biology, University of Cologne, Cologne, Germany
4. German Rheumatism Research Centre Berlin, and Charité University Medicine, Berlin, Germany
5. Hamburg Centre of Paediatric and Adolescent Rheumatology, Hamburg, Germany
6. German Centre for Paediatric and Adolescent Rheumatology, Garmisch-Partenkirchen, Germany